Question

use combinatorics to find the 5th term of (2+z)^8

Answer 1

= 8C4 2^4 *z ^4
= 1120 z ^4

Answer 2

\[\left(\begin{matrix}8 \\ 4\end{matrix}\right)\]
nCr =
\[n! \over (n - r)! r!\]
8C4 = \[8! \over (8 - 4)! 4!\]
\[8 * 7 * 6 * 5 \over4 * 3 * 2 * 1\]
8C4 = 70

Answer 3

That's your coefficient. Just plug in the numbers now :)

Answer 4

or you can use my guide here http://openstudy.com/study?login#/updates/4fb7bd6fe4b05565342d33a0

Answer 5

70(2)^4(z)^4 = 1120z